The structural similarity between hexagonal boron nitride (hBN) and graphite is highlighted by the widespread use of term “white graphite” for boron nitride. This similarity has led to the efforts of using carbon chemistry and technology as guidance for research in boron nitride chemistry and technology. Such efforts resulted in the synthesis of cubic boron nitride (cBN) based on the structure of diamond, and boron nitride nanotubes (BNNT) based on the structure of carbon nanotubes.
On the other hand, the differences in chemical bonding between graphite and hBN lead to differences in the physical properties of the materials such as electrical conductivity and reactivity to air at high temperature. The ionic interlayer bonding in hBN is much stronger than the Van der Waal force between the graphite layers causing differences in the reactivity in intercalation. This also leads to differences in the efficiency of mass producing the respective exfoliated products for engineering purposes.
A layered material is “intercalated” when other chemicals are inserted into the layers, and a layered material is “exfoliated” when the layered structure split into thinner layers. Graphite can easily be intercalated, and then exfoliated by driving intercalates out of the layers quickly and/or explosively. The process of intercalation-exfoliation of graphite has been used in many engineering applications, such as fabrication of flexible graphite, or grafoil. Recently there are reports that intercalation-exfoliation has been used to split graphite into graphene in large quantities.
The similarity between carbon and boron nitride suggests the possibility that boron nitride can be easily intercalated and exfoliated as well. However, this is not the case. Starting from hBN instead of graphite, the above process to produce large quantity of exfoliated hBN or “white graphene” has not been successful. Intercalation of hBN is difficult. Alkali metals (Li, Na, and K) and fluorosulfate (S2O6F2) are among the few intercalates that have previously been successfully intercalated into h-BN. It involves highly reactive chemicals and reactions. The feasibility of using these chemicals for mass producing exfoliated hBN or “white graphene” was not studied or discussed in these reports. The less reactive intercalates for graphite, such as metal chloride, have been found unreactive to hBN. Most notably among them is ferric chloride (FeCl3). It is generally believed that intercalation of hBN with FeCl3 in particular or metal chloride in general is not likely. For producing exfoliated hBN, the less efficient method of functionalization, sonication and centrifuge is commonly used. For “white graphene,” plasma etching or micromechanical cleavage techniques have been used for minute quantities.